Backlight asymmetric light input wedge

ABSTRACT

A backlight is disclosed and includes a visible light transmissive body primarily propagating light by TIR with a light input surface and a light output surface and a light guide portion and a light input portion. The light guide portion has a light reflection surface and a light emission surface. The light input portion has opposing side surfaces that are not parallel. One of the opposing surfaces is co-planar with either the light emission surface or the light reflection surface. A light source is disposed adjacent to the light input surface. The light source emits light into the light input portion. A reflective layer is disposed adjacent to or on the opposing side surfaces.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 12/499,165, filedJul. 8, 2009, now U.S. Pat. No. 7,941,028 which is a continuation ofU.S. Ser. No. 11/439,764, filed May 24, 2006, issued as U.S. Pat. No.7,660,509, the disclosure of which is incorporated by reference in theirentirety herein.

BACKGROUND

The present disclosure relates generally to backlights having asymmetriclight input wedges.

Optical devices employing backlights are used, for example, in displaysfor laptop computers, hand-held calculators, digital watches, cellphones, televisions and similar devices as well as illuminated signs andmany other devices.

SUMMARY

In one exemplary implementation, the present disclosure is directed to abacklight that includes a visible light transmissive body primarilypropagating light by TIR with a light input surface and a light outputsurface and a light guide portion and a light input portion. The lightguide portion has a light reflection surface and a light emissionsurface. The light input portion has opposing side surfaces that are notparallel. One of the opposing surfaces is co-planar with either thelight emission surface or the light reflection surface. A light sourceis disposed adjacent to the light input surface. The light source emitslight into the light input portion. A reflective layer is disposedadjacent to or on the opposing side surfaces.

In another exemplary implementation, the present disclosure is directedto a backlight that includes an asymmetric diverging wedge defined by anarrow end surface and a wide end surface, and opposing side surfacesthat are not parallel and extend between the narrow end and the wideend. A light source is disposed adjacent to the narrow end surface. Thelight source emits light into the narrow end surface of the divergingwedge. A light guide is optically coupled to the wide end surface. Thelight guide has a light reflection surface and a light emission surfaceand an opposing side surface is co-planar with either the light emissionsurface or the light reflection surface. A reflective layer is disposedadjacent to or on the opposing side surfaces.

In a further exemplary implementation, the present disclosure isdirected to a backlight that includes a first asymmetric diverging wedgedefined by a first narrow end surface and a first wide end surface andfirst opposing side surfaces that are not parallel and extend betweenthe first narrow end and the first wide end. A first is disposedadjacent to the first narrow end surface. The first light source emitslight into the first narrow end surface of the first asymmetricdiverging wedge. A second asymmetric diverging wedge is defined by asecond narrow end surface and a second wide end surface and secondopposing side surfaces that are not parallel and extend between thesecond narrow end and the second wide end. A second light source isdisposed adjacent to the second narrow end surface. The second lightsource emits light into the second narrow end surface of the secondasymmetric diverging wedge. A light guide is optically coupled to thefirst wide end surface and the second wide end surface. The light guidehas a light reflection surface and a light emission surface and anopposing side surface is co-planar with either the light emissionsurface or the light reflection surface. A reflective layer is disposedadjacent to or on the first and second opposing side surfaces.

These and other aspects of the subject invention will become readilyapparent to those of ordinary skill in the art from the followingdetailed description together with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those having ordinary skill in the art to which the subjectinvention pertains will more readily understand how to make and use thesubject invention, exemplary embodiments thereof will be described indetail below with reference to the drawings, in which:

FIG. 1 provides an illustrative perspective schematic view of abacklight;

FIG. 2 is a cross-sectional view of the backlight shown in FIG. 1 takenalong lines 2-2;

FIGS. 3 to 5 are cross-sectional views of alternative backlightconfigurations; and

FIG. 6 is a top plan view of another backlight configuration.

DETAILED DESCRIPTION

The present disclosure is directed to backlights having asymmetric lightinput wedges, and particularly to backlights having asymmetric lightinput wedges with specular reflective polymeric mirror film. While thepresent invention is not so limited, an appreciation of various aspectsof the invention will be gained through a discussion of the examplesprovided below.

The following description should be read with reference to the drawings,in which like elements in different drawings are numbered in likefashion. The drawings, which are not necessarily to scale, depictselected illustrative embodiments and are not intended to limit thescope of the disclosure. Although examples of construction, dimensions,and materials are illustrated for the various elements, those skilled inthe art will recognize that many of the examples provided have suitablealternatives that may be utilized.

Unless otherwise indicated, all numbers expressing feature sizes,amounts, and physical properties used in the specification and claimsare to be understood as being modified in all instances by the term“about.” Accordingly, unless indicated to the contrary, the numericalparameters set forth in the foregoing specification and attached claimsare approximations that can vary depending upon the desired propertiessought to be obtained by those skilled in the art utilizing theteachings disclosed herein.

The recitation of numerical ranges by endpoints includes all numberssubsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3,3.80, 4, and 5) and any range within that range.

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” encompass embodiments having pluralreferents, unless the content clearly dictates otherwise. For example,reference to “a layer” encompasses embodiments having one, two or morelayers. As used in this specification and the appended claims, the term“or” is generally employed in its sense including “and/or” unless thecontent clearly dictates otherwise.

The term “polymer” will be understood to include polymers, copolymers(e.g., polymers formed using two or more different monomers), oligomersand combinations thereof, as well as polymers, oligomers, or copolymersthat can be formed in a miscible blend.

A specularly reflective surface is a surface for which an incident lightray is reflected such that the reflected angle is equal to the angle ofincidence. On a practical basis, all surfaces have some deformationwhich results in some scattering of the reflected light ray and for thepurposes of this disclosure, a value of 10% of the light energy may bereflected at angles not equal to the incident angle. In manyembodiments, there is less than 1% of the light reflected at angles notequal to the incident angle.

The present disclosure is applicable to illumination assemblies, and ismore particularly applicable to backlight assemblies that provideillumination using light sources. The backlight assemblies disclosedherein can be used for general lighting purposes, e.g., to illuminate anarea, or for providing information to a viewer by selective illuminationof different areas of the assembly as in an information display. Suchassemblies are suitable for use in backlight displays, signs,luminaries, and other lighting applications that require a significantamount of light.

The light sources described herein can include any suitable lightsource. In some embodiments, the light source is a cold cathodefluorescent lamp (CCFL). In many embodiments, the light source includesone or more solid state light sources such as, discrete light emittingdiodes (LED) dies or chips with associated electrical substrate andoptionally a thermal dissipating mechanism. As used herein, the terms“LED” and “light emitting diode” refer generally to light emittingsemiconductor elements with contact areas for providing power to thediode. A III-V semiconductor light emitting diode may be formed, forexample, from a combination of one or more Group III elements and one ormore Group V elements. Suitable materials include nitrides, such asgallium nitride or indium gallium nitride, and phosphides, such asindium gallium phosphide. Other types of III-V materials can also beused, as can inorganic materials from other groups of the periodictable. In many LED embodiments, the LED is a “flip-chip” or “wire bond”LED.

LEDs can be selected to emit at any desired wavelength, such as in thered, green, blue, cyan, magenta, yellow, ultraviolet, or infraredspectral regions. In an array of LEDs, the LEDs can each emit in thesame spectral region, or can emit in different spectral regions.Different LEDs may be used to produce different colors where the colorof light emitted from the light emitting element is selectable.Individual control of the different LEDs leads to the ability to controlthe color of the emitted light. In addition, if white light is desired,then a number of LEDs emitting light of different colors may beprovided, whose combined effect is to emit light perceived by a viewerto be white.

Another approach to producing white light is to use one or more LEDsthat emit light at a relatively short wavelength and to convert theemitted light to white light using a phosphor wavelength converter.White light is light that stimulates the photoreceptors in the human eyeto yield an appearance that an ordinary observer would consider “white.”Such white light may be biased to the red (commonly referred to as warmwhite light) or to the blue (commonly referred to as cool white light).Such light can have a color rendering index of up to 100. In oneembodiment, a collection of red, blue, and green LED dies can beselectively placed in an array. The resulting emission of light is seenby an observer as colored light or “white” light, when blended togetherin concert.

In other embodiments, the radiation or light sources includes organiclight emitting diodes (OLED), vertical cavity surface emitting lasers(VCSEL), laser diodes, and the like.

The light input wedges described herein include a specular reflectivelayer that is disposed adjacent to but not in intimate contact with atleast, the diverging surfaces of the light input wedge. Since thespecular reflective layer is not in intimate contact with the lightinput wedge diverging sides, light moves out of the diverging wedgemostly via direct emission or through total internal reflection (TIR).Light that escapes through the diverging sides of the light input wedgeis then reflected via the specular reflective layer. This configurationhas been found to improve the efficiency of the light input wedge. Thespecular reflective layer can be any useful specular reflective layersuch as, for example, a metal or dielectric material. Illustrativespecular reflective metal layers or films include silvered mirrors,polished metallic or metallized surfaces.

In many embodiments, the backlight devices described herein utilize theunique and advantageous properties of multilayer optical films as thespecular reflective layer. The advantages, characteristics andmanufacturing of such films are most completely described in U.S. Pat.No. 5,882,774, which is incorporated herein by reference. The multilayeroptical film is useful, for example, as highly efficient spectralmirrors. A relatively brief description of the properties andcharacteristics of the multilayer optical film is presented belowfollowed by a description of illustrative embodiments of backlightsystems using the multilayer optical mirror film according to thepresent disclosure.

Multilayer optical mirror films as used in conjunction with the presentinvention exhibit relatively low absorption of incident light, as wellas high reflectivity for off-axis as well as normal light rays. Theunique properties and advantages of the multi-layer optical filmprovides an opportunity to design highly efficient backlight systemswhich exhibit low absorption losses when compared to known backlightsystems. Exemplary multilayer optical mirror film of the presentinvention is described in U.S. Pat. No. 6,924,014, which is incorporatedherein by reference (see Example 1 and Example 2). Exemplary multilayeroptical mirror film includes a multilayer stack having alternatinglayers of at least two materials. At least one of the materials has theproperty of stress induced birefringence, such that the index ofrefraction (n) of the material is affected by the stretching process.The difference in refractive index at each boundary between layers willcause part of ray to be reflected. By stretching the multilayer stackover a range of uniaxial to biaxial orientation, a film is created witha range of reflectivities for differently oriented plane-polarizedincident light. The multilayer stack can thus be made useful as amirror. Multilayer optical films constructed accordingly exhibit aBrewster angle (the angle at which reflectance goes to zero for lightincident at any of the layer interfaces) which is very large or isnonexistent. As a result, these polymeric multilayer stacks having highreflectivity for both s and p polarized light over a wide bandwidth, andover a wide range of angles, reflection can be achieved.

The multilayer polymeric mirror film can include tens, hundreds orthousands of layers, and each layer can be made from any of a number ofdifferent materials. The characteristics which determine the choice ofmaterials for a particular stack depend upon the desired opticalperformance of the stack. The stack can contain as many materials asthere are layers in the stack. For ease of manufacture, preferredoptical thin film stacks contain only a few different materials. Theboundaries between the materials, or chemically identical materials withdifferent physical properties, can be abrupt or gradual. Except for somesimple cases with analytical solutions, analysis of the latter type ofstratified media with continuously varying index is usually treated as amuch larger number of thinner uniform layers having abrupt boundariesbut with only a small change in properties between adjacent layers. Inmany embodiments, the multilayer polymeric mirror film includes low/highindex pairs of film layers, wherein each low/high index pair of layershas a combined optical thickness of ½ the center wavelength of the bandit is designed to reflect.

For multilayer polymeric mirror films, the desired average transmissionfor light of each polarization and plane of incidence generally dependsupon the intended use of the reflective mirror film. One way to producea multilayer mirror film is to biaxially stretch a multilayer stackwhich contains a birefringent material as the high index layer of thelow/high index pair. For a high efficiency reflective film, averagetransmission along each stretch direction at normal incidence over thevisible spectrum (400-700 nm) is desirably less than 10% (reflectancegreater than 90%), or less than 5% (reflectance greater than 95%), orless than 2% (reflectance greater than 98%), or less than 1%(reflectance greater than 99%). The average transmission at 60 degreesfrom the normal from 400-700 nm is desirably less than 20% (reflectancegreater than 80%), or less than 10% (reflectance greater than 90%), orless than 5% (reflectance greater than 95%), or less than 2%(reflectance greater than 98%), or less than 1% (reflectance greaterthan 99%).

With the design considerations described in the above mentioned U.S.Pat. No. 5,882,774, one of ordinary skill will readily appreciate that awide variety of materials can be used to form multilayer polymericreflective mirror films when processed under conditions selected toyield the desired refractive index relationships. The desired refractiveindex relationships can be achieved in a variety of ways, includingstretching during or after film formation (e.g., in the case of organicpolymers), extruding (e.g., in the case of liquid crystallinematerials), or coating. In addition, it is preferred that the twomaterials have similar rheological properties (e.g., melt viscosities)such that they can be co-extruded.

In general, appropriate combinations may be achieved by selecting, asthe first material, a crystalline or semi-crystalline material,preferably a polymer. The second material, in turn, may be crystalline,semi-crystalline, or amorphous. The second material may have abirefringence opposite of the first material. Or, the second materialmay have no birefringence, or less birefringence than the firstmaterial. Specific examples of suitable materials include polyethylenenaphthalate (PEN) and isomers thereof (e.g., 2,6-, 1,4-, 1,5-, 2,7-, and2,3-PEN), polyalkylene terephthalates (e.g., polyethylene terephthalate,polybutylene terephthalate, and poly-1,4-cyclohexanedimethyleneterephthalate), polyimides (e.g., polyacrylic imides), polyetherimides,atactic polystyrene, polycarbonates, polymethacrylates (e.g.,polyisobutyl methacrylate, polypropylmethacrylate,polyethylmethacrylate, and polymethylmethacrylate), polyacrylates (e.g.,polybutylacrylate and polymethylacrylate), syndiotactic polystyrene(sPS), syndiotactic poly-alpha-methyl styrene, syndiotacticpolydichlorostyrene, copolymers and blends of any of these polystyrenes,cellulose derivatives (e.g., ethyl cellulose, cellulose acetate,cellulose propionate, cellulose acetate butyrate, and cellulosenitrate), polyalkylene polymers (e.g., polyethylene, polypropylene,polybutylene, polyisobutylene, and poly(4-methyl)pentene), fluorinatedpolymers (e.g., perfluoroalkoxy resins, polytetrafluoroethylene,fluorinated ethylene-propylene copolymers, polyvinylidene fluoride, andpolychlorotrifluoroethylene), chlorinated polymers (e.g., polyvinylidenechloride and polyvinylchloride), polysulfones, polyethersulfones,polyacrylonitrile, polyamides, silicone resins, epoxy resins,polyvinylacetate, polyether-amides, ionomeric resins, elastomers (e.g.,polybutadiene, polyisoprene, and neoprene), and polyurethanes. Alsosuitable are copolymers, e.g., copolymers of PEN (e.g., copolymers of2,6-, 1,4-, 1,5-, 2,7-, and/or 2,3-naphthalene dicarboxylic acid, oresters thereof, with (a) terephthalic acid, or esters thereof; (b)isophthalic acid, or esters thereof; (c) phthalic acid, or estersthereof; (d) alkane glycols; (e) cycloalkane glycols (e.g., cyclohexanedimethane diol); (f) alkane dicarboxylic acids; and/or (g) cycloalkanedicarboxylic acids (e.g., cyclohexane dicarboxylic acid)), copolymers ofpolyalkylene terephthalates (e.g., copolymers of terephthalic acid, oresters thereof, with (a) naphthalene dicarboxylic acid, or estersthereof; (b) isophthalic acid, or esters thereof; (c) phthalic acid, oresters thereof; (d) alkane glycols; (e) cycloalkane glycols (e.g.,cyclohexane dimethane diol); (f) alkane dicarboxylic acids; and/or (g)cycloalkane dicarboxylic acids (e.g., cyclohexane dicarboxylic acid)),and styrene copolymers (e.g., styrene-butadiene copolymers andstyrene-acrylonitrile copolymers), 4,4′-bibenzoic acid and ethyleneglycol. In addition, each individual layer may include blends of two ormore of the above-described polymers or copolymers (e.g., blends of sPSand atactic polystyrene). The coPEN described may also be a blend ofpellets where at least one component is a polymer based on naphthalenedicarboxylic acid and other components are other polyesters orpolycarbonates, such as a PET, a PEN or a co-PEN.

In many embodiments, the multilayer polymeric reflective mirror filmalternating layers include PET/Ecdel, PEN/Ecdel, PEN/sPS, PEN/THV,PEN/co-PET, and PET/sPS, where “co-PET” refers to a copolymer or blendbased upon terephthalic acid, Ecdel is a thermoplastic polyestercommercially available from Eastman Chemical Co., and THV is afluoropolymer commercially available from 3M Company, St. Paul, Minn.

The number of layers in the film is selected to achieve the desiredoptical properties using the minimum number of layers for reasons offilm thickness, flexibility and economy. The number of layers can beless than 10,000, or less than 5,000, or less than 2,000. Thepre-stretch temperature, stretch temperature, stretch rate, stretchratio, heat set temperature, heat set time, heat set relaxation, andcross-stretch relaxation are selected to yield a multilayer film havingthe desired refractive index relationship. These variables areinter-dependent; thus, for example, a relatively low stretch rate couldbe used if coupled with, e.g., a relatively low stretch temperature. Itwill be apparent to one of ordinary skill how to select the appropriatecombination of these variables to achieve the desired multilayer film.In general, however, a stretch ratios in the range from 1:2 to 1:10 (orfrom 1:3 to 1:7) in the stretch direction and from 1:0.2 to 1:10 (orfrom 1:0.3 to 1:7) orthogonal to the stretch direction is preferred.

A backlight provides distribution of light from a light source over anarea much larger than the light source, substantially over an entireemission or output surface area of the backlight. Light often enters thebacklight along an edge surface and propagates between a back orreflective surface and the output surface from the edge surface towardan opposing end surface of the backlight by total internal reflection(TIR). In some embodiments, the backlight back surface includesstructures, e.g., dots in a pattern. A light ray encountering one ofthese structures is redirected, i.e., either diffusely or specularlyreflected, in such a manner that it is caused to exit the outputsurface. In other embodiments, backlight light is extracted byfrustration of the TIR. A ray confined within the backlight by TIRincreases its angle of incidence relative to the plane of the outputsurface and reflective surface, due to the wedge angle, with each TIRbounce. The light eventually refracts out of the output surface at aglancing angle thereto, because it is no longer contained by TIR.

FIG. 1 provides an illustrative but non-limiting perspective schematicview of a backlight 10. The backlight 10 includes a visible lighttransmissive body 15 having a light guide portion 20 and a light inputportion 30. The visible light transmissive body 15 can be formed of anyuseful light transmissive material such as, for example, glass, quartz,and/or a polymeric material. Useful polymeric material includespolyesters, polycarbonates, polyimides, polyacrylates,polymethylstyrene, silicones such as GE's Invisisil liquid injectionmoldable material, and the like. In many embodiments, the lighttransmissive body is a solid body. The visible light transmissive body15 can be formed via any useful method. In some embodiments, the visiblelight transmissive body 15 is formed via injection molding. In otherembodiments, the visible light transmissive body 15 is formed viamachining and optionally polishing of a solid slab of material.

In some embodiments, the light guide portion 20 and a light inputportion 30 form a unitary or monolithic body. In other embodiments, thelight guide portion 20 and a light input portion 30 are separate bodieshaving an interface surface 25, where the light guide portion 20 and alight input portion 30 are optically coupled together. The light inputportion 30 and the light guide portion 20 whether separate or combinedpieces can be fabricated by injection molding, casting, extrusion or bymachining solid materials or any other suitable process. The opticalcoupling material is of an appropriate index to index match the lightinput portion 30 to the light guide portion 20.

The light guide portion 20 includes a light reflection surface 22 and alight output or emission surface 24. In the illustrated embodiment, thelight reflection surface 22 and the emission surface 24 aresubstantially parallel. In other embodiments, the light reflectionsurface 22 and the emission surface 24 are substantially non-parallel.One or more optical elements can be disposed adjacent to the emissionsurface 24 as described below.

The light input portion 30 diverges from a narrow end 32. In manyembodiments, the light input portion 30 is an asymmetric divergingwedge. The light input portion 30 includes opposing side surfaces 34, 36that are not parallel and extend between the narrow end 32 (or lightinput surface) and the light guide portion 20. In some embodiments, thelight input portion 30 includes opposing side surfaces 34, 36 that arenot parallel and extend between the narrow end 32 and a wide end 31adjacent to the interface surface 25. One of the opposing surfaces 34,36 are co-planar with either the emission surface 24 or the reflectionsurface 22. In some embodiments, one of the opposing side surfaces 34 isco-planar with the emission surface 24. In other embodiments, one of theopposing side surfaces 36 is co-planar with the reflection surface 22.In many embodiments, the width ratio of the narrow end 32 to the wideend 31 (regardless of whether the interface surface 25 is presence orabsent) is around 1:2, although it can be as low as 1:1.4 for index=1.5material. In some backlight display embodiments, the narrow end has awidth in a range from 1 to 20 mm. The length of the diverging wedge orlight input portion 30 can assist in mixing light emitted from two ormore light sources emitting light into the narrow end of the light inputportion 30. In some embodiments, this length can be in a range from 5 to200 mm.

A light source (shown in FIGS. 2-5) is disposed adjacent to the narrowend 32. The light source emits light into the light input portion 30.The light source can be any useful light source as described above. Inmany embodiments, the light source is a light emitting diode (LED). Inmany embodiments, a plurality of light sources can be arranged in anarray along an opposing side 34, 36 and/or the narrow end 32, asdesired. In some embodiments, a linear array of LEDs (a plurality ofred, blue, and green light emitting diodes) are disposed along thelength of the narrow end 32.

A reflective layer (shown in FIGS. 2-5) is disposed on or adjacent tothe opposing side surfaces 34, 36. The reflective layer can be anyuseful reflective material such as, for example, a metal or dielectricmaterial. In many embodiments, the reflective layer is a multilayerpolymeric mirror film disposed adjacent to the opposing side surfaces34, 36. The multilayer polymeric mirror film is described above andreflects more than 95% of visible light incident on the multilayerpolymeric mirror film. Multilayer polymeric mirror film or any otheruseful reflective layer can be disposed along the narrow end 30 toassist in reflecting light emitted by the light source toward the lightguide portion 20. In many embodiments, the multilayer polymeric mirrorfilm is Vikuiti™ ESR film, which is available from 3M Company, St. Paul,Minn.

FIG. 2 is a cross-sectional view of the backlight 10 shown in FIG. 1taken along lines 2-2. The backlight 110 includes a visible lighttransmissive body 115 having a light guide portion 120 and a light inputportion 130. The visible light transmissive body 115 can be formed ofany useful light transmissive material as described above. In someembodiments, the light guide portion 120 and a light input portion 130form a unitary or monolithic body. In other embodiments, the light guideportion 120 and a light input portion 130 are separate bodies having aninterface surface 125, where the light guide portion 120 and a lightinput portion 130 are optically coupled together.

The light guide portion 120 includes a light reflection surface 122 anda light output or emission surface 124. In the illustrated embodiment,the light reflection surface 122 and the emission surface 124 aresubstantially parallel. In many embodiments, the light reflectionsurface 122 includes a specular and/or diffuse reflective layer 129 anda plurality of light extraction elements 127, as described above. Thelight extraction elements 127 can be arranged in any useful random ornon-random or pseudo-random pattern, as desired, to provide uniformextraction of light from the backlight. In some embodiments, theplurality of light extraction elements 127 form a pattern of dots from0.1 to 10 mm in diameter.

One or more optical elements 140 can be disposed adjacent to theemission surface 124. In some embodiments, the optical element 140includes a liquid crystal display. In other embodiments, the opticalelement 140 includes a liquid crystal display and one or more opticalfilms disposed between the liquid crystal display and the emissionsurface 124. In a further embodiment, the optical element 140 is agraphic film or other optical film. In a further embodiment, the opticalelement 140 many not be needed, for example, it the emission surface 124is used as a light source or luminaire.

The light input portion 130 diverges from a narrow end 132. In manyembodiments, the light input portion 130 is an asymmetric divergingwedge. The light input portion 130 includes opposing side surfaces 134,136 that are not parallel and extend between the narrow end 132 and thelight guide portion 120. In some embodiments, the light input portion130 includes opposing side surfaces 134, 136 that are not parallel andextend between the narrow end 132 and a wide end 131 adjacent to theinterface surface 125. In many embodiments, one of the opposing sidesurfaces 134 is co-planar with the emission surface 124. In manyembodiments, the width ratio of the narrow end 132 to the wide end 131(regardless of whether the interface surface 125 is presence or absent)is around 1:2, although it can be as low as 1:1.4 for index=1.5material. Illustrative dimensions of the light input portion 130 aredescribed above.

A light source 150 is disposed adjacent to the narrow end 132. The lightsource 150 emits light into the light input portion 130. The lightsource 150 can be any useful light source as described above. In manyembodiments, the light source 150 is a light emitting diode (LED). Insome embodiments, a linear array of LEDs 150 (a plurality of red, blue,and green light emitting diodes) are disposed along a length of thenarrow end 130.

A reflective layer 160 is disposed on or adjacent to the opposing sidesurfaces 134, 136. The reflective layer 160 can be any useful reflectivematerial such as, for example, a metal or dielectric material. In manyembodiments, the reflective layer 160 is a multilayer polymeric mirrorfilm disposed adjacent to the opposing side surfaces 134, 136. Themultilayer polymeric mirror film 160 is described above and reflectsmore than 95% of visible light incident (at all angles) on themultilayer polymeric mirror film 160. In some embodiments, themultilayer polymeric mirror film 160 reflects more than 98% of visiblelight incident at all angles on the multilayer polymeric mirror film160. Multilayer polymeric mirror film 160 or any other useful reflectivelayer can be disposed along the narrow end 132 to assist in reflectinglight emitted by the light 150 source toward the light guide portion120, however this is not required. In many embodiments, the multilayerpolymeric mirror film is Vikuiti™ ESR film, which is available from 3MCompany, St. Paul, Minn.

In many embodiments, the multilayer polymeric mirror film 160 isdisposed adjacent to the opposing side surfaces 134, 136 but is not inintimate contact with the opposing side surfaces 134, 136. In manyembodiments, an air gap 105 is defined between the multilayer polymericmirror film 160 and the opposing side surfaces 134, 136.

FIG. 3 is a cross-sectional view of an alternative backlight 210configuration. The backlight 210 includes a visible light transmissivebody 215 having a light guide portion 220 and a light input portion 230.The visible light transmissive body 215 can be formed of any usefullight transmissive material as described above. In some embodiments, thelight guide portion 220 and a light input portion 230 form a unitary ormonolithic body. In other embodiments, the light guide portion 220 and alight input portion 230 are separate bodies having an interface surface225, where the light guide portion 220 and a light input portion 230 areoptically coupled together.

The light guide portion 220 includes a light reflection surface 222 anda light output or emission surface 224. In the illustrated embodiment,the light reflection surface 222 and the emission surface 224 aresubstantially non-parallel and form a converging wedge shape. In manyembodiments, the light reflection surface 222 includes a specular and/ordiffuse reflective layer 229, as described above.

One or more optical elements 240 can be disposed adjacent to theemission surface 224. In some embodiments, the optical element 240includes a liquid crystal display. In other embodiments, the opticalelement 240 includes a liquid crystal display and one or more opticalfilms disposed between the liquid crystal display and the emissionsurface 224. In a further embodiment, the optical element 240 is agraphic film or other optical film. In a further embodiment, the opticalelement 240 many not be needed, for example, it the emission surface 224is used as a light source or luminaire.

The light input portion 230 diverges from a narrow end 232. In manyembodiments, the light input portion 230 is an asymmetric divergingwedge. The light input portion 230 includes opposing side surfaces 234,236 that are not parallel and extend between the narrow end 232 and thelight guide portion 220. In some embodiments, the light input portion230 includes opposing side surfaces 234, 236 that are not parallel andextend between the narrow end 232 and a wide end 231 adjacent to theinterface surface 225. One of the opposing surfaces 234, 236 isco-planar with either the emission surface 224 or the reflection surface222. In some embodiments, one of the opposing side surfaces 234 isco-planar with the emission surface 224. In other embodiments, one ofthe opposing side surfaces 236 is co-planar with the reflection surface222. In many embodiments, the width ratio of the narrow end 232 to thewide end 231 (regardless of whether the interface surface 225 ispresence or absent) is around 1:2, although it can be as low as 1:1.4for index=1.5 material. Illustrative dimensions of the light inputportion 230 are described above.

A light source 250 is disposed adjacent to the narrow end 232. The lightsource 250 emits light into the light input portion 230. The lightsource 250 can be any useful light source as described above. In manyembodiments, the light source 250 is a light emitting diode (LED). Insome embodiments, a linear array of LEDs 250 (a plurality of red, blue,and green light emitting diodes) are disposed along a length of thenarrow end 232.

A reflective layer 260 is disposed on or adjacent to the opposing sidesurfaces 234, 236. The reflective layer 260 can be any useful reflectivematerial such as, for example, a metal or dielectric material. In manyembodiments, a multilayer polymeric mirror film 260 is disposed adjacentto the opposing side surfaces 234, 236. The multilayer polymeric mirrorfilm 260 is described above and reflects more than 95% of visible lightincident on (at all angles) the multilayer polymeric mirror film 260. Insome embodiments, the multilayer polymeric mirror film 260 reflects morethan 98% of visible light incident at all angles on the multilayerpolymeric mirror film 260. Multilayer polymeric mirror film 260 or anyother useful reflective layer can be disposed along the narrow end 230to assist in reflecting light emitted by the light 250 source toward thelight guide portion 220, but this is not required. In many embodiments,the multilayer polymeric mirror film is Vikuiti™ ESR film, which isavailable from 3M Company, St. Paul, Minn.

In many embodiments, the multilayer polymeric mirror film 260 isdisposed adjacent to the opposing side surfaces 234, 236 but is not inintimate contact with the opposing side surfaces 234, 236. In manyembodiments, an air gap 205 is defined between the multilayer polymericmirror film 260 and the opposing side surfaces 234, 236.

FIG. 4 is a cross-sectional view of an alternative backlight 310configuration. The backlight 310 includes a visible light transmissivebody 315 having a light guide portion 320, a first light input portion330 and a second light input portion 380. The first light input portion330 and the second light input portion 380 may be the same or different.For illustration purposes, the first and second light input portions330, 380 are described similarly, but this is not required.

The visible light transmissive body 315 can be formed of any usefullight transmissive material, as described above. In some embodiments,the light guide portion 320 and the first light input portion 330 andthe second light input portion 380 form a unitary or monolithic body. Inother embodiments, the light guide portion 320 and the first light inputportion 330 and the second light input portion 380 are separate bodieshaving interface surfaces 325, where the light guide portion 320 and thefirst light input portion 330 and second light input portions 380 areoptically coupled together.

The light guide portion 320 includes a light reflection surface 322 anda light output or emission surface 324. In the illustrated embodiment,the light reflection surface 322 and the emission surface 324 aresubstantially parallel. In many embodiments, the light reflectionsurface 322 includes a specular and/or diffuse reflective layer 329 anda plurality of light extraction elements 327, as described above. Thelight extraction elements 327 can be arranged in any useful random ornon-random or pseudo-random pattern, as desired, to provide uniformextraction of light from the backlight. In some embodiments, theplurality of light extraction elements 327 form a pattern of dots from0.1 to 10 mm in diameter.

One or more optical elements 340 can be disposed adjacent to theemission surface 324. In some embodiments, the optical element 340includes a liquid crystal display. In other embodiments, the opticalelement 340 includes a liquid crystal display and one or more opticalfilms disposed between the liquid crystal display and the emissionsurface 324. In a further embodiment, the optical element 340 is agraphic film or other optical film. In a further embodiment, the opticalelement 340 many not be needed, for example, it the emission surface 324is used as a light source or luminaire.

The first light input portion 330 diverges from a narrow end 332 and thesecond light input portion 380 diverges from a narrow end 382. In manyembodiments, the first and second light input portions 330, 380 areasymmetric diverging wedges. The first light input portion 330 includesopposing side surfaces 334, 336 that are not parallel and extend betweenthe narrow end 332 and the light guide portion 320. The second lightinput portion 380 includes opposing side surfaces 384, 386 that are notparallel and extend between the narrow end 382 and the light guideportion 320. In some embodiments, the first and second light inputportions 330, 380 between the narrow end 332, 382 and a wide end 331,381 adjacent to the interface surfaces 325. One of the opposing surfaces334, 336 or 384, 386 are co-planar with either the emission surface 324or the reflection surface 322. In some embodiments, one of the opposingside surfaces 334, 384 is co-planar with the emission surface 324. Inother embodiments, one or both of the opposing side surfaces 336, 386is/are co-planar with the reflection surface 322. In many embodiments,one of the opposing side surfaces 334, 384 is co-planar with theemission surface 324. In many embodiments, both of the opposing sidesurfaces 334 and 384 are co-planar with the emission surface 324. Inmany embodiments, the width ratio of the narrow end 332, 382 to the wideend 331, 381 (regardless of whether the interface surface 325 ispresence or absent) is around 1:2, although it can be as low as 1:1.4for index=1.5 material. Illustrative dimensions of the light inputportion 330, 380 are described above.

A light source 350 is disposed adjacent to the narrow ends 332, 382. Thelight source 350 emits light into the light input portions 330, 380. Thelight source 350 can be any useful light source as described above. Inmany embodiments, the light source 350 is a light emitting diode (LED).In some embodiment, a linear array of LEDs 350 (a plurality of red,blue, and green light emitting diodes) are disposed along the length ofthe narrow end 332, 382.

A reflective layer 360 is disposed on or adjacent to the opposing sidesurfaces 334, 336. The reflective layer 360 can be any useful reflectivematerial such as, for example, a metal or dielectric material. In manyembodiments, a multilayer polymeric mirror film 360 is disposed adjacentto the opposing side surfaces 334, 336, 384, 386. The multilayerpolymeric mirror film 360 is described above and reflects more than 95%of visible light incident on the multilayer polymeric mirror film 360.In some embodiments, the multilayer polymeric mirror film 360 reflectsmore than 98% of visible light incident at all angles on the multilayerpolymeric mirror film 360. Multilayer polymeric mirror film 360 or anyother useful reflective layer can be disposed along the narrow end 330,380 to assist in reflecting light emitted by the light 350 source towardthe light guide portion 320, however this is not required. In manyembodiments, the multilayer polymeric mirror film is Vikuiti™ ESR film,which is available from 3M Company, St. Paul, Minn.

In many embodiments, the multilayer polymeric mirror film 360 isdisposed adjacent to the opposing side surfaces 334, 336, 384, 386 butis not in intimate contact with the opposing side surfaces 334, 336,384, 386. In many embodiments, an air gap 305 is defined between themultilayer polymeric mirror film 360 and the opposing side surfaces 334,336, 384, 386.

FIG. 5 is a cross-sectional view of an alternative backlight 410configuration. The backlight 410 includes a visible light transmissivebody 415 having a light guide portion 420 and a first light inputportion 430 and a second light input portion 480. The first light inputportion 430 and the second light input portion 480 may be the same ordifferent. For illustration purposes, the first and second light inputportions 430, 480 are described similarly, but this is not required.

The visible light transmissive body 415 can be formed of any usefullight transmissive material as described above. In some embodiments, thefirst light guide portion 420, first light input portion 430, and secondlight input portion 480 form a unitary or monolithic body. In otherembodiments, the first light guide portion 420, first light inputportion 430, and second light input portion 480 are separate bodieshaving an interface surfaces 425, where the light guide portion 420, thefirst light input portion 430, and the second light input portion 480are optically coupled together.

The light guide portion 420 includes a light reflection surface 422 anda light output or emission surface 424. In the illustrated embodiment,the light reflection surface 422 and the emission surface 424 aresubstantially non-parallel and form a converging wedge shape. In manyembodiments, the light reflection surface 422 includes a specular and/ordiffuse reflective layer 429, as described above.

One or more optical elements 440 can be disposed adjacent to theemission surface 424. In some embodiments, the optical element 440includes a liquid crystal display. In other embodiments, the opticalelement 440 includes a liquid crystal display and one or more opticalfilms disposed between the liquid crystal display and the emissionsurface 424. In a further embodiment, the optical element 440 is agraphic film or other optical film. In a further embodiment, the opticalelement 440 many not be needed, for example, it the emission surface 424is used as a light source or luminaire.

The first light input portion 430 diverges from the narrow end 432 andthe second light input portion 480 diverges from the narrow end 482. Inmany embodiments, the first light input portion 430 is a diverging wedgeand the second light input portion 480 is a diverging wedge. The firstlight input portion 430 includes opposing side surfaces 434, 436 thatare not parallel and extend between the narrow end 432 and the lightguide portion 420 and the second light input portion 480 includesopposing side surfaces 484, 486 that are not parallel and extend betweenthe narrow end 482 and the light guide portion 420. In some embodiments,the light input portions 430, 480 include opposing side surfaces 434,436, 484, 486 that are not parallel and extend between the narrow ends432, 482 and a wide end 431, 481 adjacent to the interface surfaces 425.One of the opposing surfaces 434, 436 or 484, 486 are co-planar witheither the emission surface 424 or the reflection surface 422. In someembodiments, one of the opposing side surfaces 434, 484 is co-planarwith the emission surface 424. In other embodiments, one or both of theopposing side surfaces 436, 486 is/are co-planar with the reflectionsurface 422. In many embodiments, one of the opposing side surfaces 434,484 is co-planar with the emission surface 424. In many embodiments,both of the opposing side surfaces 434 and 484 are co-planar with theemission surface 424. In many embodiments, the width ratio of the narrowend 432, 482 to the wide end 431, 481 (regardless of whether theinterface surface 425 is presence or absent) is around 1:2, although itcan be as low as 1:1.4 for index=1.5 material. Illustrative dimensionsof the light input portion 430, 480 are described above.

Light sources 450 are disposed adjacent to the narrow ends 432, 482. Thelight sources 450 emit light into the light input portions 430, 480. Thelight source 450 can be any useful light source as described above. Inmany embodiments, the light source 450 is a light emitting diode (LED).In some embodiment, a linear array of LEDs 450 (a plurality of red,blue, and green light emitting diodes) are disposed along a length ofthe narrow end 432, 482.

A reflective layer 460 is disposed on or adjacent to the opposing sidesurfaces 434, 436. The reflective layer 460 can be any useful reflectivematerial such as, for example, a metal or dielectric material. In manyembodiments, a multilayer polymeric mirror film 460 is disposed adjacentto the opposing side surfaces 434, 436, 484, 486. The multilayerpolymeric mirror film 460 is described above and reflects more than 95%of visible light incident on the multilayer polymeric mirror film 460.In some embodiments, the multilayer polymeric mirror film 460 reflectsmore than 98% of visible light incident at all angles on the multilayerpolymeric mirror film 460. Multilayer polymeric mirror film 460 or anyother useful reflective layer can be disposed along the narrow end 432,482 to assist in reflecting light emitted by the light 450 source towardthe light guide portion 420, but this is not required. In manyembodiments, the multilayer polymeric mirror film is Vikuiti™ ESR film,which is available from 3M Company, St. Paul, Minn.

In many embodiments, the multilayer polymeric mirror film 460 isdisposed adjacent to the opposing side surfaces 434, 436, 484, 486 butis not in intimate contact with the opposing side surfaces 434, 436,484, 486. In many embodiments, an air gap 405 is defined between themultilayer polymeric mirror film 460 and the opposing side surfaces 434,436, 484, 486.

In the illustrations discussed thus far, the backlights described hereinincluded either one or two light input portions. In some cases, it iscontemplated that three, four or more light input portions could beemployed utilizing some or all of the elements described above. FIG. 6is a schematic top view of a backlight 510 that includes a light guideportion 530 (showing the emission surface of the backlight 510). Thebacklight 510 also includes a first light input portion 542, a secondlight input portion 544, a third light input portion 546 and a fourthlight input portion 548. Each light input portion 542, 544, 546 and 548may be integrally molded or otherwise formed with the light guideportion 530. In other instances, one or more of the light input portions542, 544, 546 and 548 may be formed separately and then subsequentlyattached (optically coupled) to the light guide portion 530.

Each of the light input portions 542, 544, 546 and 548 may include oneor more light sources, including light sources 150, 250, 350 and 450 aspreviously discussed. Each light input portion 542, 544, 546 and 548 mayinclude a light source or a plurality of light sources.

The illustrated backlight 510 is shown generally having a square shape,however the backlight can have any polygonal shape and including one ormore light input portions (including the light sources) adjacent to oneor more of the polygonal sides. In some embodiments, the backlight 510has a rectangular shape with either a 4 to 3 aspect ratio or a 16 to 9aspect ratio, and can be useful in television or monitor application. Insome embodiments, the backlight 510 is used in conjunction with acommercial graphics display, or a sign.

The present invention should not be considered limited to the particularexamples described herein, but rather should be understood to cover allaspects of the invention as fairly set out in the attached claims.Various modifications, equivalent processes, as well as numerousstructures to which the present invention can be applicable will bereadily apparent to those of skill in the art to which the presentinvention is directed upon review of the instant specification.

1. An illumination assembly, comprising: an asymmetric diverging wedgedefined by a narrow end surface and a wide end surface, and opposingside surfaces that are not parallel and extend between the narrow endand the wide end; a solid state light source extending into theasymmetric diverging wedge at the narrow end surface, the solid statelight source emitting light into the narrow end surface of the divergingwedge; a light guide optically coupled to the wide end surface, thelight guide having a light reflection surface and a light emissionsurface, and one of the opposing side surfaces being co-planar from thenarrow end surface to the wide end surface with either the lightemission surface or the light reflection surface; and a reflective layerdisposed parallel with and adjacent to or on each of the opposing sidesurfaces, wherein the diverging wedge and the light guide are separatebodies coupled together at the wide end surface, and wherein the lightemission surface functions as a luminaire.
 2. The illumination assemblyof claim 1, further comprising a reflective layer on the lightreflection surface, wherein the reflective layer includes a plurality oflight extraction elements.
 3. The illumination assembly of claim 1,wherein the solid state light source comprises a light emitting diode.4. The illumination assembly of claim 1, wherein the light emissionsurface and the light reflection surface are parallel.
 5. Theillumination assembly of claim 1, wherein the light emission surface andthe light reflection surface are non-parallel.
 6. A backlight assemblyfor a sign, comprising: an asymmetric diverging wedge defined by anarrow end surface and a wide end surface, and opposing side surfacesthat are not parallel and extend between the narrow end and the wideend; a solid state light source extending into the asymmetric divergingwedge at the narrow end surface, the solid state light source emittinglight into the narrow end surface of the diverging wedge; a light guideoptically coupled to the wide end surface, the light guide having alight reflection surface and a light emission surface, and one of theopposing side surfaces being co-planar from the narrow end surface tothe wide end surface with either the light emission surface or the lightreflection surface; a reflective layer disposed parallel with andadjacent to or on each of the opposing side surfaces; and a graphic filmpositioned adjacent the light emission surface, wherein the lightemission surface provides backlighting for the graphic film.
 7. Thebacklight assembly of claim 6, further comprising a reflective layer onthe light reflection surface, wherein the reflective layer includes aplurality of light extraction elements.
 8. The backlight assembly ofclaim 6, wherein the solid state light source comprises a light emittingdiode.
 9. The backlight assembly of claim 6, wherein the light emissionsurface and the light reflection surface are parallel.
 10. The backlightassembly of claim 6, wherein the light emission surface and the lightreflection surface are non-parallel.